With a car that's out of warranty it's a mistake to take it to a main dealer. Main dealers for any brand usually replace parts rather than, in the case of the calipers, remove, scour corrosion, grease, replace. It's a common tasks on many cars, and any independent will be able to do it for you cheaply. Replacing the calipers because they need lubricating is like changing the car every time it needs an oil change.
DPF - again there are a lot of diesel specialists out there who can do this for you very quickly and for little cost. They'll also be happy to give you tips on how to avoid it becoming an issue again.
If you're unsure of something, want opinions on how best to deal with an issue, or simply want to learn more about your car and things to keep an eye on then you're in the right place. Unlike a main dealer we're not trying to get into your wallet!